Gram + Cell Wall: - Thickness - Cross-linking - Major Components - Roles of Components

Thickness: > 40 Layers Cross-linking: - Lots Major Components: - Peptidoglycan - Teichoic Acid (endotoxic effects?) - Lipoteichoic Acid (endotoxic effects?)

Outer Membrane: - Charge - Purpose of Charge - Unique Proteins - Porins

Outer Membrane Serves as an additional Permeability Barrier Charge: - Outer Membrane = NEGATIVE Purpose of Charge: - Evade Phagocytosis - Hinder Antibiotic Uptake - Avoid the action of Complement Unique Protein: - Lipopolysaccharide (LPS) Porins: - Allow Substrates to enter the periplasm

(01) Bacterial Struct And Class Flashcards by Barrett Thompson

What are the two major shapes of bacteria?

Bacilli (rods)

- Spheres (cocci)

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Define each of the following arrangements.

Strepto-
Diplo-
Staphylo-

Strepto = Chains
Diplo = Pairs
Staphylo = Grape-like Clusters

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What are the most common infectious agents?

Staphylococci

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What are group of bacteria is:

comma shaped
spiral shaped

comma = vibrio
Spiral = Spirilli

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Cell walls:

Bacteria
Animals
Plants
Fungi

Bacteria - Peptidoglycan
Animals - NONE
Plants - Cellulose
Fungi - Chitin

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Bacterial Peptidoglycan Cell wall:

Role in Pharm.
Structural Role
Classification

Pharm:
- Difference in Prokaryotes and Eukaryotes makes it an important target

Structural Role:
- Provides Rigidity

Classification:

Gram +
Gram -

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What is the difference between a Gram + and Gram - cell wall?

Gram +
- Thick and heavily cross-linked

Gram -
- Thin and lightly cross-linked

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What are the roles of Pili?

Disease:
- Attach the Bacteria to the Host Cell surface

Sex:
- Sex Pilus allows for transmission of genetic material during conjugation

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Capsules:

Job
Presence
Common in which disease?
ink

Job:
- Protect Encapsulated Bacteria From Phagocytosis

Presence:
- NOT present in all bacteria

Disease:
- Meningitis is often caused by capsulized bacteria

Ink:
- Often excludes ink such as India ink

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Spores

formed by which type?
Formed when?
Purpose?

Bacteria:
Gram + rods

When:
- Times of Stress, nutrient limitation

Purpose :
- Dehydrated and dormant, allowing potential pathogens to survive for a VERY long time

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Gram + Cell Wall:

Thickness
Cross-linking
Major Components
Roles of Components

Thickness:
> 40 Layers

Cross-linking:
- Lots

Major Components:

Peptidoglycan
Teichoic Acid (endotoxic effects?)
Lipoteichoic Acid (endotoxic effects?)

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What are Teichoic Acid and Lipoteichoic Acid?

Polymers of Glycerol Phosphate and Ribitol Phosphate

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What is the major barrier to the environment in both Gram Positive and Gram Negative Bacteria?

Cytoplasmic Membrane

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Gram - Cell Wall:

Thickness
Number of Lipid Membranes
Peptidoglycan location

Thickness:
- 2 layers of Peptidoglycan Thick

Number of Lipid Membranes:
- 2

PG Location:
- BETWEEN two lipid membranes (in periplasm)

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Outer Membrane:

Charge
Purpose of Charge
Unique Proteins
Porins

Outer Membrane Serves as an additional Permeability Barrier

Charge:
- Outer Membrane = NEGATIVE

Purpose of Charge:

Evade Phagocytosis
Hinder Antibiotic Uptake
Avoid the action of Complement

Unique Protein:
- Lipopolysaccharide (LPS)

Porins:
- Allow Substrates to enter the periplasm

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T or F: the Periplasm contains many degradative proteins.

True, these help to degrade antibiotics

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What are the components of LPS?

- purpose of each

Lipid A (endotoxin)
- toxic phospholipid
Core Polysaccharide
O Antigen
- Major Surface antigen of Gram - bacteria

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Lipid A and Septic Shock

Recognized by innate immune system and elicits CYTOKINE STORM causing septic shock

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Gram (-) Type I Protein Secretion System.

Transporter Type
From Where, To Where?
Other imp. features
Type of Bacteria with it?

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Transporter:
- ABC (ATP Binding Cassette)

From and To:
- Pumps from CYTOPLASM directly to EXTRACELLULAR SPACE

Important:
- Allows drugs to be pumped out leading to DRUG RESISTANCE

ALL GRAM (-) Bacteria

Gram (-) Type II Protein Secretion System.

Purpose
From Where, To Where?
Type of Bacteria with it?

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Purpose:
- General Secretory Pathway

From and To:
- From CYTOPLAM to PERIPLASM then to extracellular space

ALL GRAM (-) Bacteria

Gram (-) Type III Protein Secretion System.

Purpose
From Where, To Where?
Type of Bacteria with it?

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Purpose:
- Pathogenesis, DIRECT INJECTION of toxins

From and To:
Hydrophobic protein spans from CYTOPLASM of bacteria into CYTOPLASM of animal (crosses 3 membranes total)

ONLY PATHOGENIC GRAM (-) BACTERIA HAVE THIS

4 steps of Gram Staining

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Crystal Violet (color)
Gram Iodine (fixes color)
Decolorizer (EtOH or Acetone)
- color lost in gram (-) cells
Safarin Red
- colors gram (-) cells, gram (+) cells remain purple

What is formed by removal of cell walls from bacteria?

- what happens to these?

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Protoplast = bacteria w/o cell wall
Bacterial Cell Lyses happens

**This is why cell walls are an important target

Peptidoglycan

Disaccharides and arrangement
Linking Enzyme

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Repeating NAM (N-acetylmuramic acid) and NAG (N-acetylglucosamine)
Transglycoslyase = linking enzyme

Pentapeptides - linkage to sugar - linkage to other pentapeptides - enzyme?

Pentapeptides linked to the NAM (N-acetylmuramic acid) of the peptidoglycan Pentapeptides link to other pentapetides to form interstrand crosslinks Enzyme for Crosslinking: - Transpeptidases and Carboxypeptidases (aka penicillin binding proteins)

What is the difference in crosslinking between Gram (-) and Gram (+) bacteria?

In gram (+) bacteria a PENTAGLYCINE interpeptide lins the polypeptides

What is found at the terminal end of NAM-pentapeptides? - purpose - removed by?

Terminal D-alanine Purpose: - Critical to Cross-linking Process Removed by: Carboxypeptidases ***Target for antimicrobials

What do Cycloserine and Vancomycin affect? | - how do they differ?

- The D-alanine at the terminal end of the pentapeptides Cycloserine - inhibits their incorporation into the pentapeptide Vancomycin - masks their availability for crosslinking

Cell Wall Assembly (4 steps)

1. NAM and NAG are made into a disaccharide IN CYTOPLASM 2. NAM-NAG is linked to Lipid Carrier via Diphosphate bond IN CYTOPLASM 3. NAM-NAG added to growing Peptidoglycan chain after being carried across membrane by Lipid carrier 4. Lipid carrier dephosphorlyated and returns to inner leaflet

How do the following affect cell wall assembly? 1. Lysozyme 2. Bacitracin

Lysozyme: - Cleaves NAM-NAG bond Bacitracin: - Prevents dephosphorylation of disphosphate from lipid carrier so it cannot be recycled

Where can lysozyme be found?

- Tears - Saliva - Lysosomes of Phagocytotic cells

ß-lactam - resembles - Bound by - Job

Resembles: D-alanine D-alanine terminal pair Bound By: Traspeptidases (penicillin-binding proteins)

What are examples of ß-lactams?

- PENICILLIN - Cephalosporins - Carbapenems - monobactams

What is the difference between the action of ß-lactams and drugs like vancomycin?

Vancomycin bind D-alanine D-alanine while ITS STILL ATTACHED TO ITS LIPID CARRIER

What enzymes allow for resistance to be conferred against ß-lactams?

1. ß-lactamases | 2. Mutated Transpeptidases that no longer bind ß-lactams

How does Vancomycin resistance occur?

D-alanine D-lactone is synthesized - D-alanine D-lactone is not recognized by vacomycin but can still by linked by transpeptidases

* *What is required for ß-lactams to work? | - why?

CELL GROWTH - Growing Cells have AUTOLYSINS that cleave sugars for new subunit insertion - ß-lactams inhibit new cross-links from forming and the cell LYSES

What are three notable examples that cannot be stained by gram stain? - Why doesn't gram stain work? - what diseases are caused by these?

1. Mycoplasma - Lack a Cell wall - cause an atypical pneumonia in humans 2. Chlamydia - Lack Peptidoglycan - Pneumonia, Blindness, Genital infections 3. Mycobacterium - Waxy Coat containing Mycolic Acid - TB and Leprosy

How are Mycobacterium cells stained?

1. Carbol Fuchsin penetrates the waxy coat to enter the cells 2. Cells are washed using acid-alcohol (acid-alcohol destains Gram organisms) **These cells are call ACID-FAST

What are: - aerobes - anaerobes - facultative anaerobes **which account for the majority of pathogens?

Aerobes: - need O2 to live Anaerobes: - Killed in the Presence of O2 Facultative Anaerobes: - LIVE IN BOTH ENVIROMENTS ***MOST PATHOGENS ARE FACULTATIVE ANAEROBES

What type of bacteria grows in the absence of oxygen but grow optimally at low O2 concentration?

Microaerophilic bacteria

What 8 factors are used to classify bacteria?

1. Morphology 2. Arrangement 3. Staining Properties 4. Growth Properties 5. Fermentation Properties 6. Other Enzymatic and Virulence properties 7. Antigenicity 8. Genotype

What is Serotyping?

- Looking at the antigens on a given bacteria

What bacteria type is associated with the Lancefield Antigen?

Streptococcus

What method would you use to distinguish between the strains of a genus? - why would you want to do this?

Serotyping - helps determine the SOURCE and SEVERITY of the infections

Escherichia Coli O157:H7 - disease? - what does each part mean?

Causes Diarrheal outbreaks ``` Escherichia = genus Coli = species O157 = O-antigen on LIPOPOLYSACCHARIDE of the strain H7 = H antigen found on the Flagella of the strain ```

What is the most common method used to Genotype a bacteria? | - when would this be used?

RFLP (restriction fragment length polymorphism) - digest the genome to get specific fragment of different lengths - Use this during outbreaks

(01) Bacterial Struct And Class Flashcards

(47 cards)